Date issued

Feb 4, 2018 - 4:00 PM

Valid until

Feb 5, 2018 - 4:00 PM

Prepared by

Tim Haggarty

While we expect natural activity to drop off as recent storm and wind slabs settle out and the cold air takes over, the persistent slab problems still linger. Another storm in the forecast for Wednesday will provide a further test to the snowpack.

Regular season
Monday - February 5, 2018
Alpine

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Below Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Tuesday - February 6, 2018
Alpine

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Below Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Wednesday - February 7, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Below Treeline

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

Avalanche Problem 1: Persistent Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

Control work on Wednesday produced several results on this layer, particularly in the alpine where storm slabs were able to entrain enough mass to step down to mid-pack instabilities. Field teams observed Whumpfing and moderate test results Sunday.

Travel and Terrain Advice
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Avalanche Problem 2: Wind Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

Snow that began to accumulate last Sunday quickly settled into a touchy soft slab in many locations. In exposed areas, strong SW winds further developed these slabs midweek. 10-15cm of new snow that arrived Saturday and Sunday now hides these slabs.

Travel and Terrain Advice
  • If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.
  • Be cautious as you transition into wind affected terrain.

Avalanche Problem 3: Loose Dry

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

The new snow that fell Saturday and Sunday has triggered a few slabs as it has sluffed off of rock faces or steep terrain. Consider the potential for this if you enter steep or confined terrain.

Travel and Terrain Advice
  • Avoid terrain traps, such as gullies, where the consequences of a small avalanche could be serious.

Avalanche Summary

Avalanche control on Wednesday along the Icefields Parkway produced numerous size 3 avalanches in the alpine, and many size 2-2.5 storm slab and loose avalanches at all elevations. Persistent slab avalanches were produced in the alpine where wind loaded areas provided enough of a load to trigger a step down to these mid-pack layers.

Snowpack Summary

10-15 cm of new snow arrived with a Northerly flow Saturday. This sits over recent wind and storm slabs formed by 40cm of snow pushed around mainly by strong SW winds. Midpack persistent weak layers, mainly preserved Jan 7surface hoar down 40 to 60cm and the rotten Dec 15 FC sitting just below are still a concern but remain stubborn to triggering.

Weather Forecast

Warm, wet, pacific air is over-riding the cold arctic air that arrived to Jasper with a NorthWesterly flow Feb 3. A few cm of snow can be expected overnight Sunday before the cold air wins out again yielding a return to clear, mainly calm and cold through Tuesday. Forecasts call for this same pattern to bring another push of Pacific air Wednesday

Danger Ratings Explained

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Natural avalanches possible; human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

4 - High

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Natural avalanches likely; human-triggered avalanches very likely.

Large avalanches in many areas; or very large avalanches in specific areas.

5 - Extreme

Avoid all avalanche terrain.

Natural and human-triggered avalanches certain.

Large to very large avalanches in many areas.

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